Ok, I'm just getting my feet wet into this audiophile stuff. But, I love my music and want to hear in the best way possible that I can afford. I have found a really nice pair of headphones that fit my budget. However, they come in 3 different OHM's. I can get the Beyerdynamic DT 990's in 32 ohm, 250 ohm, 600 ohm. From what I understand the 32 ohm doesn't require a seperate headphone amp and can easily be driven by a pc or mp3 player. (I'll mention that all my music is in AAC 256kbps. Not quite lossless but still much better than standard 128 kbps mp3.) But the 250 ohm and 600 ohm do need an amp to get the best out of them.

My questions are:

1) how much better sounding is the 600 ohm over the 250 ohm over the 32 ohm? If any?2) Will an inexpensive headphone amp like the Fiio E7 or E11 drive the 250 ohm enough to get the sound I paid for?3) I plan on using these on my desktop computer for music (rock/metal) and gaming. Am I better off with the 32 ohm or is it worth the extra expense to get a cheap amp for the 250 ohm?

I appreciate the educated feedback as I am a complete noob and need help on this.

The freqency responce ends up being slightly different for the same model with different Ohmage as in this case. Which one is better is up to you. As a generality higher Ohmage headphones are better performing across the board. You might want a amp even if you choose a 32Ohm model for the sake of impedance matching, I doubt there is a sound card with an 8Ohm headphone outout(1:8 rule).

1) how much better sounding is the 600 ohm over the 250 ohm over the 32 ohm? If any?

Impedance doesn't relate to quality. Mostly, the difference is just that higher impedances won't be quite as loud for a given amplifier voltage, and lower impedances will be somewhat harder on an amp since they'll draw more current. For things in the 32-100 range, theres not much difference. 600 ohms might be a little quiet on some devices, depends on the sensitivity of the headphones (how loud they are per mW of power delivered).

QUOTE (aaronius @ Feb 17 2012, 02:00)

2) Will an inexpensive headphone amp like the Fiio E7 or E11 drive the 250 ohm enough to get the sound I paid for?

I think what saratoga was trying to say is that the harmonic distortion of the headphones varies with the ratio of the headphone's impedance to that of the amplifier, i.e. the 600 ohm headphones perform better from the same amplifier than the 250 ohm headphones. The amplifier is not the source of the distortion, but it affects the distortion of the headphones.

As for THD, 0.05% is way less than the best that you can get from vinyl, but you don't see audiophiles throwing away their turntables.

Those are 0 load measurements. The distortion introduced by an amplifier is approximately proportional to the load. As you noted, at zero load there is essentially 0 THD. Try those measurements again with a 16 ohm load. Then an 8 ohm load. I bet THD is >>1% then

QUOTE (IgorC @ Feb 17 2012, 11:29)

60dB. Is it much or not. It's relative. Apple cheap stock buds have noise at -40 dB. Is it much?

-60dB is basically irrelevant.

QUOTE (IgorC @ Feb 17 2012, 11:29)

These two statements have a very little sense together.

Higher impedance will introduce less load on the amp, but its ridiculous to imply that distortion 60dB below peak (or even more!) equates to quality. Its basically irrelevant compared to the performance of the headphone itself.

Those are 0 load measurements. The distortion introduced by an amplifier is approximately proportional to the load. As you noted, at zero load there is essentially 0 THD. Try those measurements again with a 16 ohm load. Then an 8 ohm load. I bet THD is >>1% then

It was a loopback between line-out and line-in. Not quite 0 load but, yes, I tend to admit that the impedance is on high side there. l take some time for detailed researchment and learning

As a generality higher Ohmage headphones are better performing across the board.

Thats not true.

Yeah, actually it's the amp that has a easier job of producing a more accurate output for higher impedance headphones. Amp issues aside the different models will have a different frequency responce which don't have hard correlation to impedance specs. The frequency responce will likely be the most audible parameter which is why you audition a phone before making a purchase.